This invention relates to the field of devices for metering agricultural seed from a seed hopper.
In the prior art, Canadian Patent No. 1,036,869 which issued Aug. 22, 1978 to Stocks for a Means For Metering Particulate Material teaches that it is known to provide a hopper mounted on a wheeled support where the floor of the hopper defines an exit closed by counter-rotatable rollers. Each of the rollers is covered with a layer of compressible material so as to provide a resilient nip between the rollers through which seed may be discharged from the hopper at a controlled rate. The device of Stocks discloses the use of a single neoprene covered roller forming a short nip between the roller and a glass metering plate, attached to the hopper, which bears against the roller. The metering plate may be mounted to the hopper by a hinge so as to allow adjustment of the position of the plate relative to the roller so as to vary the pressure of the plate bearing against the roller.
As with other conventional or prior art seed dispensers which rely on a roller or pair of rollers disposed beneath an opening in the floor of a bin, Stocks discloses allowing the seed to fall through the hole in the floor of the bin so as to accumulate in the nip a reservoir of seeds waiting to be fed through the nip by the rotation of the roller. The seed flow rate is regulated by the speed of rotation of the roller. What occurs in the prior art is that the seeds which flow into the nip may bunch or jam so that the flow rate of the seeds through the roller is not uniform.
The seed metering device of the present invention includes a roller nip beneath a seed reservoir such as a bin or hopper. The reservoir has a first aperture in a floor of the reservoir. The nip is formed by first and second opposed facing nip forming surfaces mounted beneath the first aperture so that seeds fall through the first aperture into the nip. The first nip forming surface is a radially-outer surface of a resilient roller. The second nip forming surface is a rigid control surface of a lower wall. The roller is rotatable by a roller drive in a first rotational direction so as to draw seeds down through the nip, by frictional engagement of the seeds in the nip with the surface of the resilient roller so as to slide or roll the seeds along the control surface and through the nip. The roller may be made entirely of resilient foam such as polyurethane foam. The roller surface may be either smooth or scalloped or notched transversely, for example to accommodate larger seeds. The roller drive is driven by a drive means such as a stepper motor, ground drive or other rotational drive for example acting through gearing such as reduction gearing.
An apertured slide may be slidably mounted adjacent the floor of the reservoir. The slide has a second aperture. The slide is slidably positionable into a position between an open position, wherein the second aperture is aligned with the first aperture to allow a flow of seeds from the reservoir into the nip, and a closed position wherein the second aperture is offset from the first aperture so as to block the first aperture with a seed-impervious portion of the slide.
The floor is preferably rigid and the slide may be mounted between the floor and the nip. The slide and the floor may be generally planar although this is not intended to be limiting.
In one embodiment, where restricted seed flow into the nip is desired, the second nip forming surface includes a rigid nozzle surface of a restrictor plate removably mounted beneath or in the first aperture, in which case the rigid nozzle surface may be a lower surface of a converging nozzle conduit extending through the restrictor plate so as to extend beneath the first aperture. Advantageously the restrictor plate has a curved lower surface flush with a portion of the surface of the roller and the nozzle conduit terminates in an aperture in the curved lower surface. The nozzle conduit and its corresponding aperture form a short secondary nip through which the seeds are drawn before falling into a primary nip.
In an embodiment where a greater seed flow rate is desired, the restrictor plate is removed allowing seeds to fall into the primary nip directly. The primary nip is a wedge-shaped elongate curved nip formed by the mounting of the roller in eccentric relation to a constant radius section of a lower wall of the roller housing, or otherwise forming the lower wall of the roller housing so that the primary nip extends in a curved gradually converging wedge over at least a 60 degree radiussed arc along the inner surface of the lower wall of the roller housing between generally the position of the secondary nip on the lower wall and a generally vertically aligned position on the lower wall, vertically aligned beneath the center of curvature of the lower wall, where the roller contacts the lower wall of the roller housing. In one embodiment the lower surface of the vertex of the wedge-shaped primary nip is a short flat substantially horizontal planar section or member for example formed by the use of a spreader plate. The spreader plate may have a downstream-most rolled rim-like lip providing a rounded edge as the exit surface downstream from the vertex.
In applicant""s experience, the elongate curved seed flow trajectory of seeds being drawn through the primary nip by rotation of the roller, under the softly resilient urging of the seeds against the lower wall of the roller housing by the resilient roller, tends to sort the seeds into a single seed thickness layer feeding into and through the vertex of the wedge-shaped primary nip without bunching, jamming or double-stacking of seeds, i.e. without being left as a double thickness seed layer in the nip. The use of the downstream spreader plate provides for a generally uniform xe2x80x9cwater-fallxe2x80x9d-like dispersion of seeds across the width of the spreader plate so as to result in an even curtain of falling seeds being metered from the vertex of the nip.
The roller may be mounted on a drive shaft of the roller drive. The roller may be sandwiched between a pair of rigid discs mounted one on each opposite side of the roller so as to leave the radially-outer surface of the roller exposed for rotation through the nip. In this embodiment, the pair of rigid discs are rigidly mounted on the drive shaft. The discs may be mounted to the roller by adhesive or otherwise so that rotation of the pair of rigid discs on the drive shaft simultaneously rotates the roller.
A pair of rigid walls may be mounted below the floor of the reservoir, generally orthogonal to the floor. The pair of walls may have apertures so that the drive shaft may be journalled through the apertures. The pair of walls sandwich the pair of rigid discs and the roller. In one embodiment each wall of the pair of walls has arcuate fairleads which form disc supports for sliding rotational mating of the pair of rigid discs in the disc supports.
In one aspect of the present invention, the roller may be one of a parallel array of rollers, the array of rollers extending the length of the first aperture.